This application seeks support for the "Second International Brainstorming Meeting on Parkinson disease: Nosology," scheduled for May 16th and 17th, in Louisville, KY. The main goal of this conference is to bring together world-known clinical and basic scientist experts from various research backgrounds to brainstorm on the nosology of idiopathic Parkinson's disease (PD) and refine its diagnostic criteria. There are no biological markers for the pre-mortem diagnosis of PD. PD misdiagnosis is frequent, particularly at early stages. Recent understanding of the non-motor aspects of PD and degeneration outside the substantia nigra has increased the understanding of the disorder, but these findings have also challenged current clinical diagnostic criteria. Moreover, in view of recent advances in PD genetics (i.e., alpha-synuclein triplications and duplications), it needs to be clarified if dementia is part of the spectrum of PD. Further, since some genetically determined Parkinson syndromes, sometimes closely resemble, PD, but differ from it neuropathologically; it needs to be elucidated if Lewy bodies are required for the neuropathologic PD definition. It is clear that PD is diverse clinically, pathologically, and etiologically diverse, but the various entities have not been fully agreed upon. Since only well defined populations lead to firm conclusions in genetic, epidemiologic or clinical drug trials, it is crucial, and timely, in view of current scientific advances, to reflect on the PD nosology and to redefine the set of clinical and pathologic diagnostic criteria for this disorder. International experts will cover the fields of pathology, genetics, molecular biology, movement disorders, neuroimaging, neuropsychology, neurobehavior and neuroepidemiology. This conference will also engage junior investigators to present ongoing research at poster sessions and will provide an excellent opportunity for them to interact with senior scientists. Discussions will center on current knowledge, caveats of current studies, and future research needs, providing opportunities for new collaborations and new study proposals as well as revisions of clinical and neuropathologic diagnostic criteria for PD. The results of this conference will be published in a peer-reviewed journal and it is anticipated that this will allow gaining a greater insight and understanding of PD that will help move the field forward. The PI has extensive experience in organizing this type of meetings that have led to highly cited publications in peer-review journals. This conference has the support of the Movement Disorder Society and the University of Louisville and NINDS support is critical to its success and dissemination, there are no recent or future conferences on this topic. PUBLIC HEALTH RELEVANCE: The main goal of this conference is to bring together clinical and basic scientist experts from various research backgrounds to brainstorm on the nosology of idiopathic Parkinson's disease (PD) and refine its diagnostic criteria. [unreadable] [unreadable] [unreadable]